Screw driver



M. A. WEST SCREW DRIVER April 20, 1343.

Filed Nov. 14, 1941 2 Sheets-Sheet 1 MAXWEL'L A. WEST INVENTOR.

A TORNEYS 20, 1943. WEST Y 2,317,319

SCREW DRIVER Filed Nov. 14, 1941 2 Sheets-Sheet 2 IN VENTOR.

ATTORNEYS MAXWELL A. WEST v Patented Apr. 20, 1943 SCREW DRIVER Maxwell A. West, Portland, 0reg., assignor to Champion, Inc., Portland, 0reg., a corporation of Oregon Application November 14, 1941, Serial No. 419,161

4 Claims.

This invention relates to drivers for screws of various kinds, and, in particular, relates to a screw driver such as that described in United States Letters Patent No. 2,218,631, issued under date of October 22, 1940, in which a separate bit is mounted at the end of a suitable shank in such manner that limited movement of the axes minimum, nevertheless, there will still be some wearing and occasional damaging of the bit, so that removal and replacement of the bit will be required from time to time. When the bit is attached to the driver shank by means of a pin,

in the manner shown in Patent No. 2,218,631, removal and replacement of the bit will require a certain amount of time and eifort, since this will necessitate removal of the relatively small connecting pin. I have found, however, that by making certain modifications in the driver it is possible to dispense with this pin entirely for most practical purposes, thereby making it possible to facilitate considerably the changing of the bit and increasing the saving in time afiorded by the use of the jointed driver.

The object of this invention accordingly is to provide an improved means for mounting the bit in the shank by which thenecessity for any retaining pin or any corresponding third member is dispensed with, and which will enable the bit to be retained in, place by a simple "snap-on construction, but which will still permit the freedom of movement of the bit in the shank, which freedom of movement is an essential feature of this driver as well as of the driver of Patent No. 2,218,631.

This object, and incidental advantages, I attain by making slight modifications in the walls of the recess or slots in the bit-end of the shank, and by otherwise forming the shank and bit in the manner hereinafter described with reference to the accompanying drawings.

In the drawings:

Fig. 1 is a long tudinal elevation of a screw driver illustrating an embodiment of my invention, the bit of the driver being shown in place in a screw recess;

Fig. 2 is a longitudinal elevation of the bit-end of the driver shank illustrating the contours of the sections at the end of the shank before and after the forming of this part of the driver has been completed;

Fig. 3 is an elevation, drawn to a larger scale, of the bit and lower portion of the shank of Fig. 1 illustrating the freedom of movement of the bit in the shank;

Fig. 4 is a view, in perspective, of'the end of the driver shank prior to the insertion of the bit therein;

Fig. 5 is a view, in perspective, of one form of bit adapted to be used in the driver;

Fig. 6 is an end elevation, or bottom plan view,

of the bit and shank;

Fig. 7 is a side elevation of the shank and bit.

illustrating in broken lines how bits of different size may be used;

Fig. 8 is an elevation of the end of the driver showing a slightly modified form in which my invention may be made; i I

Fig. 9 is a view of the bit of Fig. 8. drawn to slightly reduced scale;

Fig. 10 is a partial elevation illustrating a further modification of my invention; and

Fig. 11 is a view, in perspective, of another bit adapted for use in the driver and designed for driving an ordinary single-slotted screw.

The screw driver shank is indicated in general by the reference character 10, and is preferably formed with an enlarged or bulbous end or nose II. This end is bifurcated by two slots which intersect on the axis of the shank and are at right angles to each other. Thus two pairs of aligned slots l2, l2 and i3, I-3' (see Figure 4) are provided for receiving the wings l6, l5. I1, I'I' (Figure 5) or the wings 26, 2B, 28, 28 (Figure ll) of the bit. The walls of the slots are preferably slightly rounded or are beveled slightly, at their intersection, as indicated at H in Fig.

4. which may be done by axially drilling the end of the shank Ill to a depth corresponding to the depth of the slots.

It is preferable that the slots l2, l2, l3, 13"

do not extend beyond the largest diameter of the nose H of the shank, and that this nose be of sufiicient size to provide'adequate cross-sectional area and strength at the inner ends of the slots. and the cross-sectional area at this point should be preferably equal to that of the main smaller diameter portion of the shank II). By forming the shank with the enlarged or bulslots at first to have parallel side walls I5, which a are indicated in full line in Fig. 2. The width of these slots is greater than the thickness of the Wings 16, I6, l1, 11' (Fig. or the wings 26, 26,-

28, 28' (Fig. 11) of the driver bit which it is desired to use with the shank, in order to permit a certain amount of movement of the bit in the shank slots. The shank slots I2, 12', I3, I3, terminate in flat end walls l8 and I9 as shown in Fig. 4.

When the slots have been made in the ends of the shank, the resulting four quarter-sections a: at the shank end are forced inwardly toward the axis of the shank, as indicated by the broken line positions in Fig. 2, until the width of the slots at their mouth is slightly less than the thickness of the wings of the bit. This causes the slot walls to be tapered, as shown in Figs. 1, 3, 4 and 7. It is preferable, after this is done, to have the end of the shank then heat-treated and tempered to spring consistency. The shank is now ready to receive the bit. Let it be assumed that a bit A of the form shown in Fig. 5 (which form of bit is also described in co-pending application, Ser. No. 358,900, filed September 28, 1940, and entitled Driver tool), is desired to be used in the driver. The top ends of thegvings l6, l6, l1, H are beveled slightly as shown at 20 in Fig. 5 to facilitate inserting the bit into the shank. The bit A is then easily forced into the shank slots, for example, by placing the tip of the bit against a solid object, alining the wings of the bit with the shank slots, and pushing the driver shank against the, bit. When the wings of the bit are forced into the slots the surrounding quartersections of the ends of the shank are placed under tension. This tension causes the bit to be retained in the slots. Should the tension not be sufiicient a few taps with a hammer at this portion of the shank will suffice to cause the mouths of the slot walls to press against the wings of the by the mouths of the slots will not prevent lateral movement of the ends of the bit wings, and thus will not prevent the axis of the bit and the axis of the shank from being moved out of alinement nor prevent limited universal pivotal movement of the bit with respect to the shank. Thus, for most practical purposes, this means of retaining the bit in the shank will be found as satisfactory as that described in Patent No. 2,218,631. The removal of the bit with this present or snap-on construction, however, is a much simpler matter, since all that is necessary is to take hold of the bit by means of a pair of pliers or similar tool in one hand while the other hand holds the handle end of the shank, whereupon the bit can be pulled out of the shank without any difliculty.

Since the bit is slidable in the shank it is desirable, in order to facilitate the rocking of the bit in the shank, to have the top ends of the wings of the bitmade slightly convex, as indicated at y y in Fig. 3. The same result could also be obtained by making the top end of the wings flat and the inner ends l8, IQ of the shank slots slightly curved.

As indicated in Fig. 7, bits of various sizes could be used with the same shank, provided, of course, the wings of all the bits were made of uniform thickness and provided the upper ends of the wings were not made too wide for the nose of the shank.

In Fig. 8, the bit-B'isof slightly modified form in that the sides of the wings are not parallel throughout their entire extent, but are parallel only at the lower portion beyond the shank. Near the mouth of the slots the sides of each wing are offset sharply towards each other, as indicated at 2 I, so as to produce a minimum wing thickness in the mouth of the slots. The wing sides for the remaining section of each wing are then tapered outwardly, as shown at 22,'until the original normal wing thickness is reached. When the mouths of the slots in the shank are caused to-pinch the bit at the thinnest portion of the wings, the removal of the bit from the shank will be more difficult since, in removing the bit, it is necessary to overcome not only the frictional resistance exerted by the slot mouths but the quarter-sections at the end of the shank must also actually becated in broken line in Fig. 8) is drilled in theshank at the intersection of the inner ends of the shank slots. The bit knob and shank socket exert a stronger tendency for the bit to be held in axial alinement with the shank, and thus tend to prevent any possible wabbling of th bit at the start of the screw driving operation. However, the rounded engaging surfaces of knob and socket allow the bit knob to shift out of the socket easily when it is desired to operate the driver with shank and bit out of axial alinement.

In the modified bit C, shown in Fig. 10, the uniform thickness of the wings is maintained as in bit A of Figs. 1 and 3. However, a lateral indentation or groove 23 is fonned in each wing side along the line of contact with the mouth of the shank slot. The edges 24 of metal of the shank at the mouth of the slot are peened so as to enter the indentations or grooves 23. By peening these edges sufiiciently, the walls of the shank slots may even be left parallel as shown in Fig. 10, instead of being forced into the taper previously described.

While these modifications are illustrated in connection with a bit designed for a screw having a cruciform recess of special form, similar modifications could also be employed with other bits, for example, with the bit D of Fig. 11. In the bit D of Fig. 11 one pair of alined wings 26, 26' are extended to form an ordinary screw-driver taper 21, suitable for the common single-slotted screw, while the other pair of wings 28, 28' merge into the screw driver tip as shown at 29.

I have described one way in which the slots are produced in the end of the shank. There are other ways in which the slots can be produced and it is not my intention to limit this invention to any particular manner or method of making the slotted shank end or of providing means for clamping or pinching the driver bit, other than as set forth in the claims. Other modifications also'would be possible in the manner in which the engaging surfaces of bit and shank are brought into engagement at the mouth of the slots, which modifications would, however, be within the scope of my invention.

I claim:

1. In a screw driver having a shank and a movable bit inserted in the end of the shank, a pair of slots in the end of said shank intersecting at right angles on the shank axis and having their opposite walls inclined towards each other from bottom to mouth, wings on said bitcorresponding to said slots, the thickness of said wings at their inner ends being less than the width of said slots at the slot bottoms but slightly greater than the width of said slots at their mouths, and the thickness of said wings adjacent the slot mouths being approximately the same as the width of said mouths, whereby said wings will be held in said slots by engagement at the slot mouths while the greater width of said slots at their bottoms will permit limited universal movement of said bit with respect to the shank axis, and the engagement of said wings with the walls of said slots will enable turning torque to be transmitted to said bit from said shank.

2. The combination described in claim 1 with the inner ends of said wings being beveled to facilitate the forcing of the wings through the mouths of said slots when said bit is inserted in the end of said shank.

3. In a screw driver having a shank and a movable bit inserted in the end of the shank, a pair of end slots in said shank intersecting at right angles on the shank axis, said slots being narrower at the mouth than at the bottom, wings on said bit corresponding to said slots, the thickness of said wings at their inner ends being less than the width of said slots at the slot-bottoms, and the thickness of said wings adjacent the slot mouths being approximately the same as the width of said mouths, whereby said wings will be held in said slots by engagement at the slot mouths while the greater width of said slots at their bottoms will permit limited universal movement of said bit with respect to the shank axis, and the engagement of said wings with the walls of said slots will enable turning torque to be transmitted to said bit from said shank.

4. In a screw driver having a shank and a movable bit inserted in the end of the shank, slots in the end of said shank intersecting on the shank axis, said slots being narrower at the mouth than at the bottom, wings on said bit'corresponding to said slots, the thickness of said wings at their inner ends being less than the width of said slots at the slot bottoms but slightly greater than the width of said slots at their mouths, and the thickness of said wings adjacent the slot mouths being approximately the same as the width of said mouths, whereby said wings will be held in said slots by engagement at the slot mouths while the greater width of said slots at their bottoms will permit limited universal movement of said bit with respect to the shank axis, and the engagement of said wings with the walls of said slots will enable turning torque to be transmitted to said bit from said shank.

MAXWELL A. WEST. 

